Hypercapnia alters stroma-derived Wnt production to limit β-catenin signaling and proliferation in AT2 cells

Persistent symptoms and radiographic abnormalities suggestive of failed lung repair are among the most common symptoms in patients with COVID-19 after hospital discharge. In mechanically ventilated patients with acute respiratory distress syndrome (ARDS) secondary to SARS-CoV-2 pneumonia, low tidal volumes to reduce ventilator-induced lung injury necessarily elevate blood CO2 levels, often leading to hypercapnia. The role of hypercapnia on lung repair after injury is not completely understood. Here - using a mouse model of hypercapnia exposure, cell lineage tracing, spatial transcriptomics, and 3D cultures - we show that hypercapnia limits β-catenin signaling in alveolar type II (AT2) cells, leading to their reduced proliferative capacity. Hypercapnia alters expression of major Wnts in PDGFRα+ fibroblasts from those maintaining AT2 progenitor activity toward those that antagonize β-catenin signaling, thereby limiting progenitor function. Constitutive activation of β-catenin signaling in AT2 cells or treatment of organoid cultures with recombinant WNT3A protein bypasses the inhibitory effects of hypercapnia. Inhibition of AT2 proliferation in patients with hypercapnia may contribute to impaired lung repair after injury, preventing sealing of the epithelial barrier and increasing lung flooding, ventilator dependency, and mortality.

Alpha-T-catenin is expressed in peripheral nerves as a constituent of Schwann cell adherens junctions

The adherens junction component, alpha-T-catenin (αTcat) is an established contributor to cardiomyocyte junction structure and function, but recent genomic studies link CTNNA3 polymorphisms to diseases with no clear cardiac underpinning, including asthma, autism and multiple sclerosis, suggesting causal contributions from a different cell-type. We show Ctnna3 mRNA is highly expressed in peripheral nerves (e.g. vagus and sciatic), where αTcat protein enriches at paranodes and myelin incisure adherens junctions of Schwann cells. We validate αTcat immunodetection specificity using a new Ctnna3-knock-out fluorescence reporter mouse line yet find no obvious Schwann cell loss-of-function morphology at the light microscopic level. CTNNA3/Ctnna3 mRNA is also abundantly detected in oligodendrocytes of the central nervous system via public databases, supporting a general role for αTcat in these unique cell-cell junctions. These data suggest that the wide range of diseases linked to CTNNA3 may be through its role in maintaining neuroglial functions of central and peripheral nervous systems. This article has a corresponding First Person interview with the co-first authors of the paper.

Lung Injury Induces Alveolar Type 2 Cell Hypertrophy and Polyploidy with Implications for Repair and Regeneration

Epithelial polyploidization after injury is a conserved phenomenon recently shown to improve barrier restoration during wound healing. Whether lung injury can induce alveolar epithelial polyploidy is not known. We show that bleomycin injury induces alveolar type 2 cell (AT2) hypertrophy and polyploidy. AT2 polyploidization is also seen in short term ex vivo cultures, where AT2-to-AT1 transdifferentiation is associated with substantial binucleation due to failed cytokinesis. Both hypertrophic and polyploid features of AT2 cells can be attenuated by inhibiting the integrated stress response using the small molecule ISRIB. These data suggest that AT2 hypertrophic growth and polyploidization may be a feature of alveolar epithelial injury. Because AT2 cells serve as facultative progenitors for the distal lung epithelium, a propensity for injury-induced binucleation has implications for AT2 self-renewal and regenerative potential upon reinjury, which may benefit from targeting the integrated stress response.

A novel crosslinking protocol stabilizes amyloid β oligomers capable of inducing Alzheimer's-associated pathologies

Amyloid β oligomers (AβOs) accumulate early in Alzheimer's disease (AD) and experimentally cause memory dysfunction and the major pathologies associated with AD, for example, tau abnormalities, synapse loss, oxidative damage, and cognitive dysfunction. In order to develop the most effective AβO-targeting diagnostics and therapeutics, the AβO structures contributing to AD-associated toxicity must be elucidated. Here, we investigate the structural properties and pathogenic relevance of AβOs stabilized by the bifunctional crosslinker 1,5-difluoro-2,4-dinitrobenzene (DFDNB). We find that DFDNB stabilizes synthetic Aβ in a soluble oligomeric conformation. With DFDNB, solutions of Aβ that would otherwise convert to large aggregates instead yield solutions of stable AβOs, predominantly in the 50-300 kDa range, that are maintained for at least 12 days at 37°C. Structures were determined by biochemical and native top-down mass spectrometry analyses. Assayed in neuronal cultures and i.c.v.-injected mice, the DFDNB-stabilized AβOs were found to induce tau hyperphosphorylation, inhibit choline acetyltransferase, and provoke neuroinflammation. Most interestingly, DFDNB crosslinking was found to stabilize an AβO conformation particularly potent in inducing memory dysfunction in mice. Taken together, these data support the utility of DFDNB crosslinking as a tool for stabilizing pathogenic AβOs in structure-function studies.

A human scFv antibody that targets and neutralizes high molecular weight pathogenic amyloid-β oligomers

Brain accumulation of soluble oligomers of the amyloid-β peptide (AβOs) is increasingly considered a key early event in the pathogenesis of Alzheimer's disease (AD). A variety of AβO species have been identified, both in vitro and in vivo, ranging from dimers to 24mers and higher order oligomers. However, there is no consensus in the literature regarding which AβO species are most germane to AD pathogenesis. Antibodies capable of specifically recognizing defined subpopulations of AβOs would be a valuable asset in the identification, isolation, and characterization of AD-relevant AβO species. Here, we report the characterization of a human single chain antibody fragment (scFv) denoted NUsc1, one of a number of scFvs we have identified that stringently distinguish AβOs from both monomeric and fibrillar Aβ. NUsc1 readily detected AβOs previously bound to dendrites in cultured hippocampal neurons. In addition, NUsc1 blocked AβO binding and reduced AβO-induced neuronal oxidative stress and tau hyperphosphorylation in cultured neurons. NUsc1 further distinguished brain extracts from AD-transgenic mice from wild type (WT) mice, and detected endogenous AβOs in fixed AD brain tissue and AD brain extracts. Biochemical analyses indicated that NUsc1 targets a subpopulation of AβOs with apparent molecular mass greater than 50 kDa. Results indicate that NUsc1 targets a particular AβO species relevant to AD pathogenesis, and suggest that NUsc1 may constitute an effective tool for AD diagnostics and therapeutics.

Liquid-chromatographic profiling of Saponinum album (Merck)

Saponinum album (Merck) is a complex composite of triterpene saponins. It was shown that Saponinum album (Merck) dramatically enhances the toxicity of the N-glycosylase saporin from the seeds of Saponaria officinalis L. as well as the toxicity of a saporin based anti-tumor toxin. This study was intended to chromatographically profile the saponins present in Saponinum album (Merck) in order to identify saponins that determine the cytotoxicity enhancing properties of Saponinum album (Merck) on saporin. For this purpose a liquid-chromatographic profiling (HPLC) followed by ESI-TOF-MS analysis and evaluation of cytotoxicity enhancer effects of saponins from Saponinum album (Merck) was performed. This is the first study describing a liquid-chromatographic profiling of saponins from Saponinum album (Merck). Ten different saponins were isolated. There was a lot of variation observed in the cytotoxicity enhancing properties of different isolated saponins, 8 out of 10 isolated saponins showed an enhancer effect on the toxicity of saporin. Based on these results it was concluded that the cytotoxicity enhancer effect of Saponinum album (Merck) is not attributable to a single, activity determining saponin.

Enhancement of cytotoxicity of ribosome-inactivating-protein type I by saponinum album is not based on stimulation of phagocytosis

Saponinum album, a mixture of triterpenoic saponins derived from Gypsophila species, led to an increased internalization of agrostin, a ribosome-inactivating-protein (RIP) type I in U-937 cells differentiated with interferon-γ or phorbol myristate acetate. Treatment with agrostin only showed no cytotoxicity. It was hypothesized that saponinum album stimulated phagocytosis and by that the uptake of agrostin. For this purpose phagocytosis experiments with Alexa-Fluor-488-labelled 1-μm amino-latex beads and FITC-labelled Escherichia coli (K-12 strain) were performed. The results indicated no stimulation of phagocytosis by treatment with saponinum album.

The distribution of saponins in vivo affects their synergy with chimeric toxins against tumours expressing human epidermal growth factor receptors in mice

BACKGROUND AND PURPOSE

Certain saponins synergize with antitumour drugs to enhance their efficacy, but the mechanisms underlying this synergy in vivo are not well studied. Here, we describe the distribution of Saponinum album (Spn) from Gypsophila paniculata L. in mice after subcutaneous injection.

EXPERIMENTAL APPROACH

The [(3)H]-labelled Spn used for in vivo experiments was biologically active, as it still increased the cytotoxicity of a chimeric toxin in vitro. Distribution of [(3)H]-Spn was measured in BALB/c mice, with or without subcutaneous tumours in the flank. Labelled Spn was subcutaneously injected in the neck, and samples of organs, blood, urine and tumour tissue were analysed for radioactivity, 5-240 min after the injection.

KEY RESULTS

The majority of [(3)H]-Spn distributed within 10 min throughout the entire animal, with high levels of radioactivity in the urine by 30 min. No preferential accumulation in tumour tissue or other organs was observed. In tumour-bearing mice, using a sequential combination of Spn (given first) and a chimeric toxin against the epidermal growth factor receptor, ErbB1, we tested two different pretreatment times for Spn. There was high antitumour efficacy (66% inhibition of tumour growth) after 60 min pre treatment with Spn, but no significant inhibition after 10 min pre treatment with Spn.

CONCLUSIONS AND IMPLICATIONS

[(3)H]-Spn was rapidly cleared from the mice after s.c. injection, and antitumour synergy with chimeric toxins was correlated with the removal of excess Spn from tissues. Disposition of Spn in vivo may critically determine antitumour synergy with chimeric toxins.

Modified Magrath Regimens for Adults with Burkitt and Burkitt-Like Lymphomas: Preserved Efficacy with Decreased Toxicity

Burkitt and Burkitt-like lymphomas are rapidly growing tumors which require specialized therapy. Although intensive, multi-agent regimens have been effective in children, results are more variable in adults. Magrath et al. previously described a regimen that was highly effective in children and young adults. This phase II study of a modified Magrath regimen was designed to assess its efficacy in older adults and reduce treatment-related toxicity. Fourteen patients with Burkitt/Burkitt-like lymphoma and median age of 47 years were stratified into two categories: low-risk (normal LDH and a single focus of disease measuring less than 10 cm, 3 patients) and high risk (all other, 11 patients). Low-risk patients received three cycles of modified CODOX-M (cyclophosphamide, doxorubicin, adriamycin, vincristine with intrathecal methotrexate and cytarabine followed by high-dose systemic methotrexate, regimen A). High-risk patients received four alternating cycles of regimens A and B (A-B-A-B). Regimen B consisted of ifosfamide, cytarabine, etoposide and intrathecal methotrexate (IVAC). The modified treatment regimen was associated with no grade 3/4 neuropathy and only one episode of grade 3/4 mucositis. All patients completed protocol therapy and there were no treatment-related deaths. Twelve patients (86%, 90% CI: 61 97%) achieved a complete response; 1 patient achieved a PR and 1 patient died of progressive disease. Nine patients (64%) are alive and disease free at a median follow-up of 29 months. This modified Magrath regimen is effective and well-tolerated in a representative group of older adult patients.

Enhancement of saporin cytotoxicity by Gypsophila saponins--more than stimulation of endocytosis

Saporin is a type I ribosome-inactivating protein with N-glycosidase activity. It removes adenine residues from the 28S ribosomal RNA resulting in inhibition of protein synthesis. Recently we have shown that saporin exerts no cytotoxicity on seven human cell lines. However, the combination of saporin with a special mixture of Gypsophila saponins (Soapwort saponins) from Gypsophila paniculata L. (baby's breath) rendered saporin to a potent cytotoxin comparable to viscumin, a highly toxic type II ribosome-inactivating protein. In this study we investigated whether the enhancement of the saporin-cytotoxicity by Gypsophila saponins is mediated by a saponin-triggered modulation of endocytosis, exocytosis or impaired degradation processes of his-tagged saporin ((his)saporin) in ECV-304 cells. For this purpose (his)saporin was labelled with tritium and cytotoxicity of the toxin alone and in combination with Gypsophila saponins was scrutinized. The transport and degradation processes of (his)saporin were not different in Gypsophila saponin-treated and control cells. However, after ultracentrifugation of a post-nuclear supernatant the amount of cytosolic (his)saporin was significantly higher in saponin-treated cells than in cells, which were only incubated with (his)saporin. This indicates a saponin mediated endosomal escape of saporin.

Soapwort saponins trigger clathrin-mediated endocytosis of saporin, a type I ribosome-inactivating protein

Saporin, a type I ribosome-inactivating protein (RIP), removes adenine residues from the 28S ribosomal RNA as part of a process that leads to inhibition of protein synthesis. However, as shown in this study, neither saporin nor his-tagged saporin (both 0.6-6 pM) exert toxicity on several human cell lines including H-2171, SK-N-SH, HEP-G2, MOLT-3, THP-1, HL-60 and ECV-304. Saporin and his-tagged saporin became highly cytotoxic when they were used in a combined treatment with Soapwort saponins (SA). When combined with SA (2-4 microg/ml) saporin became as cytotoxic as the highly toxic type II RIP rViscumin reflected by an IC50 of 42.5x10(-12) M for saporin and 21.5x10(-12) M for rViscumin. We demonstrated that saporin was internalized via clathrin-mediated endocytosis, followed by the release into the endosomal transport system. Our results indicate that SA triggers this endocytic event rendering the otherwise cell membrane impermeable type I RIP saporin a potent cytotoxin. This effect was not cell line-specific suggesting that saporin exploits a common SA-dependent mechanism to enter cells.

Evidence for an oncogenic role of AHI-1 in Sezary syndrome, a leukemic variant of human cutaneous T-cell lymphomas

Ahi-1 (Abelson helper integration site 1) is a novel gene frequently activated by provirus insertional mutagenesis in murine leukemias and lymphomas. Its involvement in human leukemogenesis is demonstrated by gross perturbations in its expression in human leukemia cells, particularly in cutaneous T-cell lymphoma cell lines where increases in AHI-1 transcripts of 40-fold are seen. To test directly whether deregulated expression of AHI-1 contributes to their transformed properties, knockdown of AHI-1 expression in Hut78 cells, a cell line derived from a patient with Sezary syndrome (SS), was performed using retroviral-mediated RNA interference. Retroviral-mediated suppression specifically inhibited expression of AHI-1 and its isoforms in transduced cells by 80% and also reduced autocrine production of interleukin (IL)-2, IL-4 and tumor necrosis factor-alpha (TNFalpha) by up to 85%. It further significantly reduced their growth factor independence in vitro and the ability to produce tumors in immunodeficient mice. Interestingly, aberrant expression of AHI-1, particularly truncated isoforms, was present in CD4+CD7- Sezary cells from some patients with SS. Elevated expression of IL-2 and TNFalpha was also found in these cells. These findings provide strong evidence of the oncogenic activity of AHI-1 in human leukemogenesis and demonstrate that its deregulation may contribute to the development of SS.

Enhancement of cytotoxicity of lectins by Saponinum album

Saponinum album, a mixture of saponins with an aldehyde function bound at C4 from Gypsophila species, increased the cytotoxicity of lectins like agrostin and saporin by enhancing its penetration through the cell membrane. The effect was attenuated by latrunculin, an inhibitor of endocytosis, and by bafilomycin, an inhibitor of transport from early to late endosomes and lysosomes. In contrast, the effect was not influenced by brefeldin A that causes dissolution of the Golgi stacks and by the addition of different monosaccharides. The toxicity of other peptidic toxins was only slightly enhanced by the saponins indicating a specific interaction between lectins and saponins present in Caryophyllaceae.

Diagnosis and treatment of Helicobacter pylori infection among California Medicare patients

BACKGROUND

Antibiotic treatment of Helicobacter pylori infection in active peptic ulcer disease has been demonstrated to speed ulcer healing, reduce the risk of rebleeding, and prevent long-term recurrence. The objective of this study was to determine whether Medicare patients with peptic ulcer disease who are admitted to acute care hospitals are being tested or treated for H pylori infection as recommended by a National Institutes of Health consensus panel.

METHODS

The study was designed as a retrospective medical records survey. From the Medicare National Claims History File, all persons 65 years and older admitted to California fee-for-service hospitals for peptic ulcer disease in 1994 were identified. A random sample of 600 claims was selected for review. After exclusions, 524 patients were eligible for study. The main outcome measures were (1) the proportion of patients who were tested for H pylori infection by 1 of the 5 available methods (histopathologic study, urease assay, microbiologic culture, serum antibody testing, or urea breath test) and (2) the proportion who were treated with antibiotics (amoxicillin, tetracycline, clarithromycin, or metronidazole) for H pylori infection.

RESULTS

Thirty-nine percent of patients with peptic ulcer disease were tested for H pylori infection and 3% were treated empirically. Only 47% of the patients who had a positive diagnostic test result for H pylori were treated with antibiotics.

CONCLUSION

Because diagnosis and treatment of H pylori infection has been demonstrated to improve outcomes and decrease expenses, the data indicate a substantial opportunity to improve the care of elderly Medicare patients with peptic ulcer disease.

Strain-specific transgene methylation occurs early in mouse development and can be recapitulated in embryonic stem cells

A murine transgene, HRD, is methylated only when carried in certain inbred strain backgrounds. A locus on distal chromosome 4, Ssm1 (strain-specific modifier), controls this phenomenon. In order to characterize the activity of Ssm1, we have investigated developmental acquisition of methylation over the transgene. Analysis of postimplantation embryos revealed that strain-specific methylation is initiated prior to embryonic day (E) 6.5. Strain-specific transgene methylation is all-or-none in pattern and occurs exclusively in the primitive ectoderm lineage. A strain-independent pattern of partial methylation occurs in the primitive endoderm and trophectoderm lineages. To examine earlier stages, embryonic stem (ES) cells were derived from E3.5 blastocysts and examined for transgene methylation before and after differentiation. Though the transgene had already acquired some methylation in undifferentiated ES cells, differentiation induced further, de novo methylation in a strain-dependent manner. Analysis of methylation in ES cultures suggests that the transgene and endogenous genes (such as immunoglobulin genes) are synchronously methylated during early development. These results are interpreted in the context of a model in which Ssm1-like modifier genes produce alterations in chromatin structure during and/or shortly after implantation, thereby marking target loci for de novo methylation with the rest of the genome during gastrulation.

The bulk chromatin structure of a murine transgene does not vary with its transcriptional or DNA methylation status

The DNA methylation status of HRD, a murine transgene, can be controlled by the genetic background upon which it is carried. We found the transgene to be transcribed in competent tissues only when undermethylated. Chromatin structure over the transgene was assayed by nuclear accessibility with DNase I, MspI, and PstI. While the transgene was up to fivefold more resistant to MspI when methylated than when not methylated, we observed no such difference with DNase I or PstI. We suggest that methyl-CpG-binding proteins are responsible for the difference observed with MspI, but that the chromatin structures are otherwise similarly compacted. Methylation could, therefore, play a regulatory role in gene expression beyond that which can be accomplished by bulk chromatin structure alone.

Influence of CpG methylation and target spacing on V(D)J recombination in a transgenic substrate

We have previously described a line of transgenic mice with multiple head-to-tail copies of an artificial V-J recombination substrate and have shown that the methylation of this transgene is under the control of a dominant strain-specific modifier gene, Ssm-1. When the transgene array is highly methylated, no recombination is detectable, but when it is unmethylated, V-J joining is seen in the spleen, bone marrow, lymph nodes, and Peyer's patches but not in the thymus or nonlymphoid tissues, including brain tissue. Strikingly, in mice with partially methylated transgene arrays, rearrangement preferentially occurs in hypomethylated copies. Therefore, V-J recombination is negatively correlated with methylated DNA sequences. In addition, it appears that recombination occurs randomly between any two recombination signal sequences within the transgene array. This lack of target preference in an unselectable array of identical targets rules out simple mechanisms of one-dimensional tracking of a V(D)J recombinase complex.

Rearrangement and expression of immunoglobulin genes in transgenic mice

Transgenic mice are discussed which carry a rearrangement test transgene. The methylation status of the transgene varies, depending on the background mouse strain. When the transgene is bred into the C57BL/6 strain, it is completely methylated and not rearranged in lymphoid organs. After several generations of crossing into DBA/2 or SJL the transgene becomes unmethylated and rearranges at high frequency. A strain specific modifier of DNA methylation (Ssm-1) was mapped close to the Friend virus susceptibility locus (Fv-1) on mouse chromosome 4. Rearranged transgenes from spleen, bone marrow and thymus of adult mice or fetal liver were cloned and sequenced. A great variety of joints was found, with about 1/3 being in the correct reading frame. Small deletions into the V- and J-coding ends as well as N region additions contributed to the variability. The fetal joints showed no N regions. Since no functional immunoglobulin (Ig) gene can be created from this artificial test gene, the data indicate that the rearrangement mechanism of the fetus differs from that of the adult.

Biologic and immunohistochemical analysis of macrophage interleukin- 1 alpha, - 1 beta, and tumor necrosis factor production during the peritoneal exudative response

The present study examined changes in lipopolysaccharide (LPS)-induced interleukin 1 (IL-1) and tumor necrosis factor (TNF) production by murine peritoneal macrophages during the chronic exudative response to Freund's complete adjuvant (CFA). Macrophages were isolated by peritoneal lavage and adherence at intervals over a 32 day period following i.p. injection of CFA. Optimal culture conditions for IL-1 and TNF production were predetermined, and it was found that IL-1 production was profoundly impaired at densities of above 150 cells/mm2, whereas TNF synthesis was more resistant to density effects. Using optimal conditions, we observed a sequential appearance of monokines. On day 0 there was minimal IL-1 production and no detectable TNF production. By days 4-7, IL-1 production reached maximum levels with a steady decline to baseline by day 32. TNF production steadily increased after day 2, reached maximal levels by days 16-20, and then partly declined by day 32. These findings were supported by kinetic analyses at specified days. When related to exudative events, it appeared that maximal IL-1 was associated with the recruitment stage of the reaction, whereas TNF production was associated with the established exudate. Immunohistochemical analysis revealed that TNF production could be related to the proportion of macrophages with cytoplasmic TNF expression. In contrast, IL-1 alpha and -1 beta expression was comparable among populations with 85-100% of cells showing cytoplasmic expression 6 hr after LPS stimulus. Whereas cytoplasmic IL-1 alpha persisted for the 18 hr study period, IL-1 beta disappeared from many adjuvant recruited cells. Our findings suggest that monokine production is orchestrated during macrophage recruitment and activation at sites of chronic inflammation.